Recently, a photovoltaic power generation using solar energy which is limitless, environment-friendly, and clean has been attracting much attention.
With reference to FIG. 12, the following explains components of a solar battery used in a photovoltaic power generation system.
As shown in FIG. 12, a solar cell SEL1000 which generates, by the photovoltaic effect, an electric current upon irradiation with sunlight is the minimum unit of a solar battery.
A solar battery module MOD1011 is a unit consisting of a plurality of solar cells SEL1000.
A solar battery string STR1001 consists of a plurality of solar battery modules MOD1011 connected in series.
A solar battery array ARR1010 consists of a plurality of solar battery strings STR1001 connected in parallel.
Next, with reference to FIG. 13, the following schematically explains a typical configuration of a photovoltaic power generation system for carrying out photovoltaic power generation.
As shown in FIG. 13, a photovoltaic power generation system 1001 includes the solar battery array ARR1010, a power conditioner 1020, and a load 1030.
The power conditioner 1020 converts a direct current power from the solar battery array ARR1010 into an alternating current power by a built-in inverter 1021 and supplies the alternating current power to the load 1030.
The photovoltaic power generation system 1001 may be configured to operate in connection with a commercial power line 1040 provided by an electric power company as shown in FIG. 13, or may be configured to operate independently of the power line 1040 provided by an electric power company.
Conventionally, in such a photovoltaic power generation system, there has been requested a more efficient conversion from solar energy to a power. In order to meet such a request, various techniques have been proposed. Four examples of such techniques are described below.
Initially, there has been proposed a technique for operating each string of solar batteries at its maximum power point (Patent Literature 1).
Furthermore, there has been proposed that each PV module (panel) is provided with a communication device for communicating with a management unit, the communication device transmits the operation state of the PV module to the management unit, and the management unit transmits to the communication device a control signal which instructs the PV module to operate at the maximum output (Patent Literature 2).
Patent Literature 3 discloses a technique in which even if a part of a photovoltaic power generation system is under different sunshine conditions, is positioned in different directions, and/or is put under different temperature conditions, switching control is made in each PV module to adjust an operating voltage/current, thereby more efficiently obtaining a power.
Lastly, Patent Literature 4 discloses that various parameters at the time when a power from a solar battery reached the maximum power point as a result of changing an operating voltage of an inverter are stored in a database, and in a normal operation, the operating voltage is adjusted based on the parameters stored in the database.